A total of over two hundred pharmacologically active alkaloids have been detected and characterized in skin extracts from some fifty species of dendrobatid frogs. These consist of six batrachotoxins (steroidal), fifteen histrionicotoxins (spiropiperidines), eighteen pumiliotoxin A class (6-alkylidene-8-hydroxy-8-methylindolizidines), one homopumiliotoxin A-calss (6-alkylidene-8-hydroxy-8-methylquinolizidines), sixteen allopumiliotoxin-A class (6-alkylidene-7,8-dihydroxy-8-methylindolizidines), six tricyclic gephyrotoxins (perhydrobenzoindolizidines), four bicyclic gephyrotoxins (indolizidines), and six pumiliotoxin C-class (decahydroquinolines). Three novel tricyclic amidine alkaloids have been characterized. About 135 alkaloids cannot be rigorously assigned to any structural group. Some 70 of these alkaloids are bicyclic tertiary amines as shown by deuteroammonia chemical inonization mass spectrometry and probably represent pyrrolizidines, indolizidines, and quinolizidines. Some seven unclassified a alkaloids which are secondary amines appear to be deoxyhistrionicotoxins. Dendrobatid alkaloids have now been characterized in phyllogenetically distinct amphibians, namely in skin extracts from a Brazilian toad, a Malagasy frog and two Australian Burrowing frogs. Inhitition of binding of radioactive batrachotoxinin benzoate to sites on the sodium channel correlates with local anesthetic activity of a wide range of drugs. The positive inotropic and chrontropic effects of pumiliotoxin B and congeners on atria are strongly dependent on the nature of the sidechain, and the lack of requisite structural features yields a cardiac depressant.